This invention relates to rotary irrigation sprinklers, and more particularly, to an infinitely adjustable by-pass opening for controlling of the speed of rotation of a turbine operated rotary sprinkler.
Water turbine rotary irrigation sprinklers, particularly of the pop-up type, having met with wide spread use in the irrigation industry, particularly where there is a need to irrigate large areas such as golf courses, parks, ball fields, and the like. Typically, such a sprinkler includes a housing that is adapted to be buried in the ground and attached to a pressurized water supply line, and a pop-up riser having one or more spray nozzles at one end, and a water driven turbine at the other. Disposed between the turbine and the nozzle is a speed reducing drive mechanism that converts the high-speed rotation of the turbine into lower speed nozzle rotation. The most common drive mechanism is that employing a gear reduction motor (typically referred to as a “gear drive” sprinkler), although there are also commercially available turbine drive sprinklers employing a ball-motor type mechanism. Exemplary of such sprinklers are the sprinklers sold by Rain Bird Corporation, the assignee of the present invention, under its designations, respectively, “T-BIRD” and “R-50.” As used herein after, the designation “rotor” is intended to refer to any of the types of rotary irrigation sprinklers employing a water driven turbine coupled to a sprinkler nozzle through a speed reducing drive mechanism, although for purposes of discussion, the following will center around such rotors employing a gear drive mechanism.
There are many situations where it is desirable to be able to change the rate of nozzle rotation of a rotor. For example, in summer high heat conditions when the rotors are to be used for “cooling” the turf, it is desirable to use a very high rate of nozzle rotation, typically on the order of one revolution per minute or less, so as to cover the irrigated area in a short time. On other occasions, such as when irrigating in very dry conditions, it is desirable to have the rate of sprinkler rotation be relatively slow, such as on the order of five revolutions per minute as to achieve maximum distance of throw. In many situations, in order to adjust the rate of sprinkler rotation, the supply line pressure is controlled, and/or the size of the sprinkler nozzle is selected to achieve the desired rate of rotation.
Another way to control the rate of sprinkler rotation is to control the amount of energy supplied to the sprinkler turbine. In many rotors, pressure controlled by-pass openings are provided to permit a portion of the pressurized water to be directed around, rather than through, the turbine. The greater the amount of by-passed water, the less that flows through the turbine, thereby controlling the speed of turbine rotation, and hence, the speed of rotation of the sprinkler nozzle. Typically, however, these by-pass openings are controlled by pressure operated valves designed to achieve a relatively constant speed of sprinkler rotation, regardless of the pressure of the supplied water. Such pressure controlled by-pass valves are disclosed, for example, in U.S. Pat. Nos. 4,625,914; 4,892,252; and 5,695,123.
Hunter Industries of San Marcos, Calif., also commercially sells a line of rotors designated by its Model Nos. G-90 and G-95, and which employ settable by-pass openings intended to permit the speed of turbine rotation to be matched with the nozzle size and supply pressure. In these sprinklers, a stator sleeve having a half-circle by-pass opening in its radial face is secured to the riser below the turbine so that incoming pressurized water can be by-passed around a central passageway leading to the turbine. Concentrically mounted within and below the stationary stator is a settable stator sleeve, similarly having a half circle opening. The settable stator sleeve has a radially outwardly projecting key that is adapted to mate with one of a plurality of discrete keyway recesses formed in the side wall of the stationary stator sleeve. By manually removing the settable stator sleeve and repositioning it with its key positioned in one of the several discrete keyways within the stationary stator, the extent of the opening for by-pass flow can be selected in discrete increments from essentially a very small opening to a complete half circle opening. Notably, however, the settable stator sleeve can not be precisely adjusted to an infinite number of settings, but is confined to the preset locations of the keyway recesses in the stationary stator. Accordingly, only a very gross rotation rate adjustment is possible and limited by the number of discrete keyway recesses formed in the stationary stator sleeve.
It has been found, that in large irrigation projects, for example on golf courses, it is very desirable to be able to precisely adjust the speed of rotation of a rotor nozzle so that uniform irrigation over large areas is possible. One problem that has arisen is that as rotors age with use, they tend to slow in their rate of rotation at a given supply pressure. When used for golf course irrigation, even a relatively small rate of ration change from one rotor to another can have very dire consequences. Accordingly, there exists a need for rotors having the capability of quick, easy, and precise adjustment of the speed of rotation of the turbine so as to be able to precisely adjust the speed of nozzle rotation within small limits. As will become apparent hereinafter, the present invention satisfies that need in a novel and unobvious manner.